Locus equations as phonetic descriptors of consonantal place of articulation

This experiment tested whether locus equation coefficients, slope, and y-intercept could serve as indices of place of articulation for obstruents sharing the same place of articulation across different manner classes. Locus equations for 22 speakers were derived from CV/t/ words with initial voiced stop /d/, voiceless aspirated stop /t/, nasal /n/, voiced fricative /z/, and voiceless fricative /s/ preceding 10 vowel contexts. Post hoc tests revealed /d/ = /z/ = /n/ for slope means. Voiced /d/ and voiceless /t/ were also equivalent when F2 transition onset measurement points were equated. Scatterplots of locus equation coefficients revealed three nonoverlapping and distinct clusters when the diverse coronal group was compared with labials and velars. A discriminant analysis using slope and y-intercept as predictors successfully categorized all five coronals into one alveolar group with 87.1% accuracy. The collective results support the contention that locus equations can serve as effective phonetic descriptors of consonant place of articulation across manner classes.